qt5.qtwebengine: fix missing GN dependency

This missing dependency does not result in a build failure
in every case. Without the dependency, there is a race
condition in the build system that is only exposed when
the build can utilize more cores.

See https://bugs.gentoo.org/933368 for context.

pkgs/development/libraries/qt-5/modules/qtwebengine-fix_build_pdf_extension_util.patch

@@ -0,0 +1,11 @@
+# From https://933368.bugs.gentoo.org/attachment.cgi?id=896907
+--- ./src/3rdparty/chromium/qtwebengine/browser/pdf/BUILD.gn.orig	2024-07-03 13:49:13.812285886 +0100
++++ ./src/3rdparty/chromium/qtwebengine/browser/pdf/BUILD.gn	2024-07-03 13:51:45.789966941 +0100
+@@ -6,6 +6,7 @@ source_set("pdf") {
+   ]
+ 
+   deps = [
++    "//chrome/app:generated_resources",
+     "//content/public/browser",
+   ]
+ }

pkgs/development/libraries/qt-5/modules/qtwebengine.nix

@@ -157,6 +157,10 @@ qtModule (
         stripLen = 1;
         extraPrefix = "src/3rdparty/";
       })
+
+      # Fix race condition exposed by missing dependency
+      # https://bugs.gentoo.org/933368
+      ./qtwebengine-fix_build_pdf_extension_util.patch
     ];
 
     postPatch =